Hi,
some of my multi-threaded programs don't print everything they should.
I have for example a small program to show that LinuxThreads don't
behave like real POSIX threads concerning "fork()" (only the thread
which creates a child process can wait for its termination with
LinuxThreads). When I run the program on Solaris I get the following
output:
gorbag work 23 fork_thr !!!! Solaris
Thread thr_fork: forking a child process.
Child process: I'm sleeping for 2 seconds.
Thread thr_wait: sleeping for 5 seconds.
Thread thr_fork: sleeping for 10 seconds.
Child process: terminating.
Thread thr_wait: try to wait for child process.
Thread thr_wait: child terminated.
Thread thr_fork: try to wait for my child. !!!!!! missing in Cygwin
Thread thr_fork: No child processes !!!!!! missing in Cygwin
gorbag work 24
When I compile and run the program on Cygwin the last output from
"thr_fork" will not be displayed. I've upgraded Cygwin to the latest
version yesterday. "cygcheck -c" displays that all packages are OK. Cygwin
is installed on Windows XP with all updates excluding SP2.
eiger src 4 fork_thr
Thread thr_fork: forking a child process. !!!! Cygwin
Thread thr_wait: sleeping for 5 seconds.
Thread thr_fork: sleeping for 10 seconds.
Child process: I'm sleeping for 2 seconds.
Child process: terminating.
Thread thr_wait: try to wait for child process.
Thread thr_wait: child terminated.
eiger src 5
A search in the mailing list and on the web wasn't successful (lots of
results which weren't related to my problem). I've split the sleeping
time of thr_fork in a loop in one second parts to see when the thread
terminates.
eiger src 11 fork_thr
Thread thr_fork: forking a child process.
Thread thr_wait: sleeping for 5 seconds.
Thread thr_fork: sleeping for 10 seconds.
Child process: I'm sleeping for 2 seconds.
Thread thr_fork: 1 s of sleeping time passed
Thread thr_fork: 2 s of sleeping time passed
Child process: terminating.
Thread thr_fork: 3 s of sleeping time passed
Thread thr_fork: 4 s of sleeping time passed
Thread thr_wait: try to wait for child process.
Thread thr_wait: child terminated.
eiger src 12
In my opinion it has something to do with the thread implementation in
Cygwin. Does anybody know why thr_fork dies when thr_wait terminates?
Thank you very much for any suggestions in advance.
That's the program without testing "ret".
--- snip ------------------------------------------------------------
/* gcc -o fork_thr fork_thr.c -lpthread */
#define _REENTRANT /* must precede any "#include"! */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <errno.h>
#include <pthread.h>
void thr_fork (void);
void thr_wait (void);
pid_t fork_pid; /* ID of child process */
int main (void)
{
int ret; /* return value of a function */
pthread_t thr_id [2]; /* ID's of created threads */
ret = pthread_create (&thr_id [0], NULL,
(void * (*) (void *)) thr_fork,
(void *) 0);
ret = pthread_create (&thr_id [1], NULL,
(void * (*) (void *)) thr_wait,
(void *) 1);
ret = pthread_join (thr_id [0], NULL);
ret = pthread_join (thr_id [1], NULL);
return 0;
}
void thr_fork (void)
{
int i;
printf ("Thread thr_fork: forking a child process.\n");
fork_pid = fork ();
switch (fork_pid)
{
case -1: /* error: no process created */
perror ("fork failed");
errno = 0;
break;
case 0: /* child process */
printf ("Child process: I'm sleeping for 2 seconds.\n");
sleep (2);
printf ("Child process: terminating.\n");
exit (0);
break;
default: /* parent process */
printf ("Thread thr_fork: sleeping for 10 seconds.\n");
for (i = 1; i < 11; i++)
{
sleep (1);
printf ("Thread thr_fork: %d s of sleeping time passed\n", i);
};
printf ("Thread thr_fork: try to wait for my child.\n");
if (waitpid (fork_pid, NULL, WNOHANG) == -1)
{
perror ("Thread thr_fork");
errno = 0;
}
else
{
printf ("Thread thr_fork: child terminated.\n");
};
};
}
void thr_wait (void)
{
printf ("Thread thr_wait: sleeping for 5 seconds.\n");
sleep (5);
printf ("Thread thr_wait: try to wait for child process.\n");
if (waitpid (fork_pid, NULL, WNOHANG) == -1)
{
perror ("Thread thr_wait");
errno = 0;
}
else
{
printf ("Thread thr_wait: child terminated.\n");
};
}
-- snip -------------------------------------------------------------
Kind regards
Siegmar
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